1. Field of the Invention
The present invention relates to an organic electroluminescent (EL) panel, an organic EL display, an organic EL lighting device, and production methods thereof. More particularly, the present invention relates to an organic EL panel that can be preferably used in an organic EL display or an organic EL lighting device, and to an organic EL display, an organic EL lighting device, and production methods thereof.
2. Description of the Related Art
According to a conventional organic EL panel, deterioration of an organic EL element, caused by the organic EL element being exposed to oxygen, moisture, and the like, is prevented by the following sealing can structure commonly used: a desiccant is attached to a sealing can (concave glass can) and a sealing resin is arranged into a frame shape to surround an organic EL element. However, it is difficult to provide the organic EL panel having this sealing can structure with a top-emission structure because in the top-emission structure, light is outputted from an upper surface of the panel (i.e., an increase in aperture ratio is difficult), and further, a reduction in thickness of the panel is also difficult. Hence, research and development on a sealing structure where a flat substrate is used (hereinafter, also referred to as a “flat sealing structure”) are now being made.
According to this flat sealing structure, a film of an adhesive free from air bubbles is formed into a specific pattern between a panel substrate (element substrate) including an organic EL element and a sealing substrate facing the panel substrate, thereby attaching the substrates to each other. If air bubbles are generated inside the adhesive, the air bubbles might deteriorate the organic EL element. Organic EL panels having such a flat sealing structure have been disclosed as follows. According to the following organic EL panel having a flat sealing structure (refer to Japanese Kokai Publication No. 2003-178866, for example), a protective barrier (sealing material) is arranged on an attachment surface of a sealing substrate to intercept a luminous area and its peripheral electrode region of a panel substrate, and an uncured sealing resin (filler) is applied on the inner side of the protective barrier on an attachment surface of the panel substrate, and the panel substrate is attached to the sealing substrate with the protective barrier and the cured sealing resin. Further, according to the following sealing process aiming at simplification of steps (refer to Japanese Kokai Publication No. 2006-179352, for example), only a solid sealing resin instead of the liquid sealing resin (filler), which needs the protective barrier (sealing material), is used to cover each light-emitting region on a panel substrate. In addition, according to the following organic EL panel (refer to Japanese Kokai Publication No. 2004-265615, for example), an organic EL element is formed on a panel substrate, and a solid sealing resin that is a cohesive sheet made of a butyl rubber is arranged to cover and surround the organic EL element, and a sealing resin made of a UV curable epoxy resin and the like is arranged to further surround the solid sealing resin.
According to the organic EL panels in Japanese Kokai Publication No. 2003-178866 and Japanese Kokai Publication No. 2004-265615, two sealing members (corresponding to the protective barrier (sealing material) and the sealing resin (filler) in Japanese Kokai Publication No. 2003-178866, or the solid sealing resin and the sealing resin including UV curable epoxy resin and the like in Japanese Kokai Publication No. 2004-265615) are arranged as a member for sealing the organic EL element. However, the two sealing members are arranged with no space therebetween. Further, according to an organic EL panel produced by the sealing process in Japanese Kokai Publication No. 2006-179352, only a sheet-like solid sealing resin is formed as the member for sealing the organic EL element. So, in the organic EL panels in Japanese Kokai Publication No. 2003-178866 to Japanese Kokai Publication No. 2004-265615, a space is slightly generated at an interface between the protective barrier or the sealing resin and the substrate when the protective barrier or the sealing resin is cured and shrinks or when the substrates warp in high temperature and humidity environments, and due to this slight space, the entire sealing member is easily separated from the substrates. As a result, moisture, oxygen, and the like, pass through the space between the sealing member and the substrate and enter the inside of the organic EL element to deteriorate the organic EL element. Thus, the organic EL elements disclosed in Japanese Kokai Publication No. 2003-178866 to Japanese Kokai Publication No. 2004-265615 still have room for improvement.
The liquid sealing resin (filler), which is arranged on the inner side of the protective barrier (sealing material) to cover each light-emitting region on the panel substrate, as in Japanese Kokai Publication No. 2003-178866, has a low viscosity in order to improve wet-spreading property inside the protective barrier. The sealing resin is surrounded and sealed by the protective barrier although the sealing resin generates a great amount of gas when being cured, and so the generated gas deteriorates the organic EL element, and a non-light-emitting region, what is called dark spot, is generated, and as a result, the light emission cannot be maintained. Thus, the organic EL panel in Japanese Kokai Publication No. 2003-178866 needs to be improved in terms of its lifetime.
In addition, if an organic EL element that includes only a solid sealing resin as a member for sealing an organic EL element is used as an organic EL element having a top-emission structure, as in Japanese Kokai Publication No. 2006-179352, the solid sealing resin needs to have transparency, and so the solid sealing resin cannot include spacers and the like. So, it is difficult to keep a thickness (gap between the substrates) or pattern shape of the solid sealing resin constant, and uneven display that is caused by a variation in characteristics or interference fringes, due to transmittance change, is generated. In order to solve these problems, a gap-controlling member such as a photo spacer needs to be formed on either one of the substrates. Thus, there is still room for improvement.
In order to seal the gap between the substrates with the solid sealing resin free from air bubbles, the sealing needs to be performed under a vacuum condition or under a combination of reduced pressure condition and heating. Accordingly, the method in which only the solid sealing resin is used as the sealing member as in Japanese Kokai Publication No. 2006-179352 needs an apparatus for attaching the substrates under the above-mentioned conditions. So, also in terms of simplification of the apparatus, improvement in alignment accuracy of the substrates (suppression of misalignment caused by a variation in temperature), such a method has room for improvement.